The present invention relates to a method for compensating the interference magnetic field of an object by means of an interference field controlled magnetic self-protection system having a winding connected to receive a magnetic field producing current and oriented to produce a magnetic field tending to compensate the interference magnetic field.
DE-OS [Federal Republic of Germany Laid-Open application] No. 2,929,964 discloses a method applied to objects such as ships wherein measured magnetic field gradients are integrated and utilized, by way of a closed control circuit, to generate a compensation current. The control process is completed as soon as the measured magnetic field gradient has become zero.
The interference magnetic field is described via three coordinates. It can be assumed that there is no general limitation with a cartesian coordinate system. In this coordination system, the magnetic field has two horizontal components Hx and Hy as well as the vertical component Hz. The abbreviated form .DELTA. Hz, should present the rate of change in space of the magnetic field via the length .delta.z (.DELTA. Hz Hz (x1, y1, z1)-Hz(x1, y1, z1+.delta.z).
Magnetic field gradient probes are placed wherever probe zero coincides with the zero location of one's own field. If no such location can be found, a settable constant or field dependent effect is superposed over the probe measuring effect to compensate for the zero difference.
This prior art method still has certain drawbacks, e.g. the fact that variable object magnetizations cannot be compensated to a sufficient degree and, in the case of malfunctions, satisfactory emergency operation is not possible.